Grundlagenuntersuchungen zum Tangentialdreschwerk

Although the state of research about the tangential threshing device is extensive there are further questions about design and adjustment of multi drum systems with considerable more parameters. For improving the efficiency and particularly with regard to the harvesting quality still lots of outstanding issues exist and additional research is necessary. The breakage of grain is an important topic especially for germination, suitability and for storage which influences the selling price. Both the design and the adjustment cause a conflict of aims in view of separation, threshing and broken grain which should be minimized. Because of this conflict of aims the question of extending the adjustment parameters of the concave clearance became more interesting to reduce or solve this problem. Therefore experimental investigations with a variable adjustment of the pre and main concave have been done with a new test rig which has got three degrees of freedom for each concave. With this adjustment system an individual course of the concave clearance can be achieved. Even though the circumferential velocity of the threshing drum and the throughput are the dominant parameter the adjustment of the concave has significant influence on threshing losses and broken grain. An increasing intensity by a rising circumferential velocity or a decreasing concave clearance causes a growing percentage of broken grain. It can be shown, that there is a strong dependence between height as well as frequency of impact and breakage. That is one reason for further investigation on the topic breakage to develop a method to analyze broken grain which is the basis for a breakage model. This model has to simulate a realistic rebound at high impact velocities and to cover the mechanical/ strength properties of grain. For this purpose modeling the static and dynamic strength behavior is necessary. With a new test impact rig load velocities between 15 and 50 m/s can be achieved to simulate dynamic load and to analyze the durability of wheat. With this result a new DEM simulation model can be created and verified as a fundament for future development of harvesting technology.